The present invention relates to a drainage pump for use in an electric washing machine, and more particularly, to a drainage pump which is suitable for use in draining a liquid containing elongated fibers such as thread waste or cloth waste.
Conventional drainage pumps have been disclosed in the specifications of, for example, Japanese Patent Laid-Open Publication No. 54-131101, Japanese Patent Publication No. 47-43241, Japanese Utility Model Publication No. 53-47204, Japanese Utility Model Laid-Open Publication No. 59-19994 and U.S. Pat. No. 3,130,679.
However, in each of the drainage pumps of the above-described type, when a liquid containing elongated fibers such as thread waste, which have a small specific gravity is drained, the fibers tend to attach onto vanes of an impeller or to gather at a center of the vanes. It is difficult to remove the fibers from the vanes and to discharge them from the pump. Furthermore, such thread waste gathers in a clearance between the impeller and a casing of the pump thereby disabling the rotation of the vanes.